Tape backup is wonderful when it
comes to cheap storage. Furthermore Wait! There is nothing else
good to say about tape backup. It is fraught with magnetic bits falling
off the plastic, stretching, heads going out of alignment, accidental
erasure, and the list goes on. The challenge then becomes how to preserve
the maximum amount of information for the longest time possible, with
the minimum number of tapes.

Two popular backup strategies
are:

Towers of Hanoi

Grandfather-Father-Son

Towers of Hanoi421 are based on a puzzle where you start out with all
the rings on one pole and must move all the rings to another pole. You
can never have a ring on top of one that is smaller than itself. The
idea is that you must move them in a certain order to accomplish the
task. The order of movement of rings is:

A-B-A-C-A-B-A-D-A-B-A-C-A-B-A-E-A-B-A-C-A-B-A-D-A-B-A-C-A-B-A-F-

A-B-A-C-A-B-A-D-A-B-A-C-A-B-A-E-A-B-A-C-A-B-A-D-A-B-A-C-A-B-A-G-

A-B-A-C-A-B-A-D-A-B-A-C-A-B-A-E-A-B-A-C-A-B-A-D-A-B-A-C-A-B-A-F-

A-B-A-C-A-B-A-D-A-B-A-C-A-B-A-E-A-B-A-C-A-B-A-D-A-B-A-C-A-B-A-H

In the case of tape backup, label
the tapes A-H and use the same order to rotate tapes through a tape
drive, each day putting a complete backup on the tape. The Towers of
Hanoi backup strategy is often used because it creates the longest possible
data retention period (the length of time archived data is kept around)
with the minimum number of tapes. For example, using the Towers of
Hanoi backup strategy with a set of 10 tapes allows for retrieval of
data up to 1023 days old.

In the Grandfather-Father-Son method,
you label tapes by the day of the week with a different tape for each
Friday in the month and a different tape for each month of the year.
Using a tape for Saturday and Sunday is optional depending on whether
you have files updated over the weekend. This would look like the following:

MONDAY TUESDAY WEDNESDAY
THURSDAY FRIDAY1

MONDAY TUESDAY WEDNESDAY
THURSDAY FRIDAY2

MONDAY TUESDAY WEDNESDAY
THURSDAY FRIDAY3

MONDAY TUESDAY WEDNESDAY
THURSDAY MONTH1

MONDAY TUESDAY WEDNESDAY
THURSDAY FRIDAYI

MONDAY TUESDAY WEDNESDAY
THURSDAY FRIDAY2

MONDAY TUESDAY WEDNESDAY
THURSDAY FRIDAY3

MONDAY TUESDAY WEDNESDAY
THURSDAY MONTH2

MONDAY TUESDAY WEDNESDAY
THURSDAY FRIDAY1

MONDAY TUESDAY WEDNESDAY
THURSDAY FRIDAY2

MONDAY TUESDAY WEDNESDAY
THURSDAY FRIDAY3

MONDAY TUESDAY WEDNESDAY
THURSDAY FRIDAY4

MONDAY TUESDAY WEDNESDAY
THURSDAY MONTH1

Because, some months have more than
four weeks, it will take over 20 tapes for regular backups.

Now that you have a backup, the question
becomes where to put it? That is tackled next.

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